Round steel rockshafts of tubular or solid cross section are commonly utilized to control height on implement frames and disk gang attachments. Bearing block assemblies typically support the shaft from a frame, and a hydraulic cylinder rotates the rockshaft to raise and lower the frame or gang. The bearing block assemblies include a two-piece cast iron or welded steel bearing block which allows rotation about an axis but limit movement in the direction of the axis. As the rockshaft rotates, often under very heavy loading, wear occurs between the steel rockshaft and the metallic bearing block. Although the bearing blocks often include a grease fitting for lubrication to reduce the wear, the hostile operating environment results in contamination of the lubricant with dust and sand which accelerates the wear. To purge the contaminants from between the rockshaft and bearing block, frequent over-greasing is required to discharge the contaminants. This greasing process is often inconvenient because of the location of the assemblies in hard to reach areas and is time-consuming and messy.
A further problem inherent with many bearing block assemblies for large applications such as agricultural implement lift systems is one of manufacturing tolerances of the shafts and of the cast iron or welded steel bearing blocks. A loose or sloppy fit between the mating parts resulting from the tolerances, combined with excessive wear that is commonly encountered in the hostile operating environment, can result in functional problems for the lift systems. Rotating rockshafts retained by bearing blocks have high wear points between the contact members. This wear requires maintenance at a prescribed interval to lubricate these joints to reduce the wear and maintain smooth operation.
Some implements use a one piece plastic liner to reduce wear. However, the one piece liner is difficult to replace if worn or damaged. In commonly assigned U.S. Pat. No. 6,932,512, a two-piece wear insert is described for eliminating greasing and reducing friction between the rockshaft and bearing block. The two-piece liner is easier to replace than a one-piece liner. However, such a liner does not provide thrust protection to accommodate side loads on the rockshaft and reduce friction and noise generated from the side loads.